Tobacco-smoke filter and method of making same

ABSTRACT

A filter for tobacco smoke consisting of clay, kaolin or feldspars or like aluminum silicate minerals which have been rendered substantially electropositive by an initial cleaning step, preferably by electrodialysis or electrolytic treatment, followed by a cationizing step in which the cationic material is adsorbed onto the mineral particles. The particles may also be rendered suitable for the filtration of tobacco smoke by subjecting them to an electrophoresis or electrolysis whereby the electronegativity is reduced.

United States Patent Gansloser 1 Mar. 21, 1972 54] TOBACCO-SMOKE FILTER AND 3,513,640 5 1970 Moliskey ..l31/265 ux METHOD OF MAKING SAME 2,839,065 6/1958 Milton ..13l/l 1,972,718 9/1934 Sharlit ..131/3l lnvemofl a 399 Consjance, Germany 3,434,479 3/1969 Till et al... ..131/1o.9 Assigneez wachs Trostbrucke Germany ThOmS l 3 [22] Filed: 1970 Primary Examiner-Melvin D. Rein 2 APP] 11 2 Att0rneyl(arl F. Ross [57] ABSTRACT [52] U.S. Cl ..13l/262, 131/107, 204/180 P,

252/457 A filter for tobacco smoke consisting of clay, kaolin or feld- 51 1111.01. ..A24f 13/06 Spars or like aluminum Silicate minerals hi h h been [58] Field of Search ..l31/9, 10l0.9, r n r substantially electropositive by an initial cleaning 131/261-269; 204/180 P; 252/410 T; 55/101, 524, step, preferably by electrodialysis or electrolytic treatment, 424 followed by a cationizing step in which the cationic material is adsorbed onto the mineral particles. 7 [56] References Cited The particles may also be rendered suitable for the filtration of UNlTED STATES PATENTS tobacco smoke by subjecting them to an electrophoresis or electrolysis whereby the electronegativity is reduced. 2,108,860 11/1934 Kauffman ..l31/262 A UX 3,013,987 12/1961 Castor et al. l 3 1/262 A UX 8 Claims, 2 Drawing Figures Silicate-Containing Natural Mineral (Clay, Fair/spar, K.1olin) f 11 Crushing/Washing Siffing b7 Acid Dist H 0 ilecfrodialysis Rqoeafed Washing (aThode Wifh Disfilled H 0 I 17 as t 50 29 Z igicafe-Mineral Parficles Caflonic R 22 Organic oyesfuff Cafionizing/ Dr in Cigereffe- Cigar-Pipe Filfer \zs I Smoke- PATENTEUMARZT I972 3,650,279

SiIicafe-Confaining Natural Mineral (Clay, Feldspar, Kaolin) f 17 Crushing/ Washing Siffing 31 15 $2 fi Z7 2 15 Dist H o U Elecfrod'al 51s 2 K I y I -14 Rqoeafed Washing *QPaThode Wifh DISH/led HgO H O+I0n5 I 17 55 CB 30 29 39 19 SiIicafe-Mineral Parficles 27 g fi Rinsing Z2 rganic Dyestuff 23 lCafionizing/Drging k 2 1i Cigareffe- Cigar-Pipe 'QH Filfer SiIicafe-Mineral Parficles CeIiu/ose Fiber 15 Cellulose Fiber +SiIicafe-Minerai Parf-iclas Helmuf Gansloser Tobacco INVI'IWI'UI-i. Fig.2

ATTORNEY TOBACCO-SMOKE FILTER AND METHOD OF MAKING SAME FIELD OF THE INVENTION The present invention relates to tobacco-smoke filters, a method of making filter material therefor and, more particularly, to improved filters for incorporation in or use with cigarettes, cigars, pipes and the like in which a stream of tobacco smoke is orally induced through a filter designed to remove undesirable components from the smoke stream.

BACKGROUND OF THE INVENTION In recent years, the concern of smokers with the possible presence of cancer-inducing components of tobacco smoke and other unhealthful and undesirable substances therein has led to the development of various filtering materials for incorporation in or use with cigarettes, cigars and pipes.

These filters, primarily designed to remove nicotine and the tarry components of cigarette smoke from the latter prior to its induction into the buccal cavity, have been incorporated in cigarettes as so-called filter tips, have been provided for replaceable use in cigarette and cigar holders, have been built into throwaway holders for cigars and the like and have been proposed for incorporation in the stems of pipes.

In general, such filters include cellulosic fibers or the like, designed to entrap and absorb moisture and condensable components of tobacco smoke, alone or together with activated carbon widely used as an adsorbant prior to the advent of such filters.

It has been found, however, that such filters do not, in fact, remove each of the undesirable components of the smoke stream or, especially components known to induce cancer and other disorders, nor are they effective to eliminate a major amount of tars from the smoke.

It has long been desired, therefore, and the object of many research projects of considerable cost, to provide a tobaccosmoke filter which is particularly effective against tars and possible cancer-inducing decomposition products such as 3, 4-

benzpyrene present in cigarette smoke, while not eliminating therefrom the essential taste sensations sought by tobacco smokers.

OBJECTS OF THE INVENTION It is, therefore, an important object of the present invention to provide a tobacco-smoke filter wherein the aforementioned disadvantage can be eliminated and which constitutes a considerable improvement over prior art filtering devices in precisely those fields in which improvement was sought.

A more specific object of this invention is to provide a tobacco-smoke filter suitable for use in or with cigarettes, cigars and pipes having improved tar-removal capabilities and effectiveness.

Still another object of this invention is the provision of a method of making improved filtering materials of the character described.

I SUMMARY OF THE INVENTION The foregoing objects and others which will become apparent hereinafter are attained, in accordance with the present invention, with a filtering material for tobacco smoke which consists at least in part of silicate-containing naturalmineral particles, preferably of the clay and feldspar type. After much investigation I have found that, surprisingly, silicate-containing natural minerals, such as clay (e.g., kaolin) and feldspars are highly effective in adsorbing tarry components of tobacco smoke and indeed are far more effective for this purpose than for the adsorption of impurities of other gas streams. In fact, while it is known to use silicate systems for the adsorption of impurities from liquid or gas streams, the silicate-containing natural minerals with which the present invention is concerned, have not been found hitherto to be particularly effective for this purpose but have been discovered by me to produce totally surprising results when incorporated in or constituted as a filtering mass for tobacco smoke after treatment as described below.

According to the present invention therefore, silicate-containing natural minerals such as clay, feldspar and kaolin, can be shaped into a porous body in the absence of the aforementioned cellulosic fibers. In either case, the filtering body can be employed as a filter tip" in a cigarette, provided as a replaceable insert for pipes or cigarettes and cigars. It may be mentioned that substantially all of the feldspars, such as orthoclase, microline, labradorite, albite, andesine, anorthoclase or anorthite, have been found to be effective for the purposes of the present invention. These minerals are characterized by an aluminum-containing silicate structure with or without alkali or alkaline-earth metals in addition thereto.

While applicant does not wish to be bound by any theory or reason for the surprising effectiveness of these particular natu ral minerals, but used in conjunction with tobacco-smoke filters, it may be hypothesized that the tarry constituents of the smoke have a particular affinity for the aluminum silicate lattice structure. It has been found, moreover, that these naturally occurring minerals are most effective when used in tobacco-smoke filters after a preliminary treatment designed to eliminate from the particles of silicate-containing mineral a characteristic negative charge. It is believed that such minerals in their naturally occurring state, are contaminated with salts which ionize in the presence of moisture with anions remaining in or on the silicate lattice while their cations are wholly or partially stripped therefrom. This fact can be demonstrated by electrolysis of a dispersion or suspension of the mineral particles from whence it can be observed that the particles drift or migrate toward the positive electrode.

I have discovered that this residual negative charge is related to the apparent inactivity of the silicate containing mineral as an adsorptive agent in tobacco-smoke filters. Thus, while silicate-containing minerals can be used in place of activated carbons in tobacco filters with improved results, these results can be improved still further by eliminating the negative charge of the silicate lattice. It is, accordingly, an important aspect of the present invention that the silicate-mineral particles are treated or cleaned to eliminate or reduce this characteristic negative charge.

According to a feature of this invention, the silicate-mineral particles are freed from the adherent negatively-charged ions by a treatment in aqueous medium, preferably in a dispersion or suspension. The treatment may be carried out in several ways or by a combination of the several techniques. Thus it is possible to reduce markedly the negative charge upon the silicate-mineral particles by agitating them with distilled water and changing this water a number of times. In this manner, the soluble salts giving rise to the negatively charged ions are dissolved partially in the distilled water. Alternatively, the particle can be treated one or more times with dilute acid or by subjecting them to electrical process (electrophoresis or electrodialysis); an electrodialysis treatment, in which a suspension of the silicate-containing mineral is subjected to the influence of a direct current applied across a semipermeable membrane is preferred.

According to another feature of the present invention, the silicate-containing particles are treated with macromolecular cations for rendering the particles generally elcctropositive. Thus the invention also contemplates the neutralization of any residual electronegative character of the particles by depositing thereon macromolecular elcctropositive materials in slight excess over the electronegative character, to impart to the particles a net elcctropositive character.

Best results are obtained when the macromolecular cations are cationic organic dyestuff bases or mordants, preferably methylene blue and FeSO.,. The electropositive particles have a significantly greater absorbtive capacity than the untreated particles presumably because of the polar character of the tarry substances whose adsorption is desired.

DESCRIPTION OF THE DRAWING The above and other objects, features and advantages of present invention will be apparent from the following specific Example and description, reference being made to the accompanying drawing in which:

FIG. 1 is a diagram illustrating the method of the present invention; and

FIG. 2 is a diagrammatic cross-sectional view through a tobacco-smoke filter embodying the invention.

SPECIFIC DESCRIPTION Referring first to FIG. 2, in which I show a cigarette-tip filter, it can be seen that the filter tip is generally defined by a paper sleeve 40 which encloses the adsorptive material and, possibly, the tobacco 41 of the cigarette adjacent the filter. Upon induction of smoke into the buccal cavity (arrow 50), the tarry products are first adsorbed and absorbed by a first filter section consisting of cellulose fiber 42 in which are dispersed particles 43 of the treated silicate-containing natural mineral. Residual tars are then carried by the smoke to a second section consisting of closely packed but porous particles 44 of the silicate-containing mineral. A further section 45 of cellulose fiber recessed at 46 from the end of the filter, is disposed between the particles 44 and the mouth and serves to absorb and entrap residual tars, condensates etc.

The silicate-containing natural mineral used in the filter of FIG. 2, which can also be incorporated in cigarettes, cigars and cigar and cigarette holders and pipes, can be produced as shown in the flow diagram of FIG. 1. The silicate-containing natural mineral (e.g., clay, feldspar or kaolin) is separated from impurities at and fed via line 11 to the crushing stage 12 in which the mineral is crushed, washed and sifted for grading to the desired particle size. The particles can range in size from tenths of a millimeter to several millimeter depending upon the desired porosity, whether or not cellulose fibers are to be provided and the length of the filter body. It has been found that a particle size of about 0.5 mm. is effective in cigarette filters of the type shown in FIG. 2.

The aluminum-silicate mineral particles of stage 12 are then treated for removing or reducing its naturally occurring negative charge. Preferably, the particles are led via line 13 to the electrodialysis or electrophoresis apparatus. The apparatus may comprise a vessel 14 subdivided by a permselective or semipermeable membrane into an anode compartment and a cathode compartment. In the cathode compartment distilled water is circulated or repeatedly changed via ducts l6 and 17, while the silicate-mineral particles are introduced into the anode compartment. A direct current is applied between the anode I9 and the cathode l8 and it is observed that cations, which are believed to have been previously adherent to the particles 20 drift toward the cathode l8 and migrate through the semipermeable membrane whereupon they are removed with the water in the cathode compartment. The anode and cathode can be composed of platinum, stainless steel or another inert material and the voltage of say, less than 10 volts can be applied thereacross. The voltage should be less than that at which substantial gas evolution occurs although the current density will vary depending upon the contamination of the mineral particle introduced into the system. A current density (in terms of electrode area) of about 0.5 amp/cm. has been found satisfactory in a specific instance when feldspar particles of the indicated particles size were used. The electrodialysis process is continued until substantially complete removal of the adherent charge and this can be discovered optically since the uncharged mineral particles are readily separated from the suspension. Thus, the electrodialysis is terminated when the particles settle to the bottom of the vessel. When electrophoresis techniques are used, the current is terminated when the particles no longer migrate toward the anode.

The particles are removed from the vessel 14 after treatment as indicated by line 2] and rinsed at stage 22 prior to being introduced at 23 into a cationizing and drying stage 24;

in the latter, the particles are treated with macromolecular cationic organic dye bases, then dried and incorporated or shaped into filters at 25. The organic dye bases need be present only in an amount slightly above any residual electronegative character of the silicate-mineral particles.

Alternatively, the crushed particles from stage 12 can be subjected to an acid wash in stage 27, 28 and 29 with dilute acid (e.g., nitric acid), at pH 5. The particles are then fed (line 30) to the rinsing stage 24 for treatment as described earlier. In still another modification of the process, the particles from stage 12 are led (line 31), together with distilled water from line 32, through a plurality of agitation and washing stages (I, II, III n). The washing stages 33 are followed by cationizing and drying with the product then being incorporated into the filter at 25 The product illustrated in FIG. 2 and produced as described with reference to FIG. I is found to have a substantially greater adsorptive capacity for nicotine and tarry products of cigarette smoke. Comparisons of the improved filter with filterless cigarettes have shown that 75 percent of the total nicotine and chloroform-soluble tarry products of cigarette smoke are removed. A filter efficiency of this level has not been attained heretofore to my knowledge.

In relative terms, the unprocessed silicate minerals, especially kaolin, has been found to have high electronegativity as evidenced by the rate at which the particles migrate to the positive electrode when subjected to a DC field. This corresponds to negligible absorptivity and absorptivity with respect to cigarette smoke. Kaolin processed by electrodialysis or electrolytic treatment as described above manifests weak electronegativity and somewhat improved filter effectiveness. While even unprocessed kaolin (i.e., kaolin which has not been subjected to either electrodialysis or electrolytic treatment) manifests somewhat reduced electronegativity when treated with the electropositivizing compounds mentioned earlier (e.g., methylene blue or FeSOO and, therefore, greater filter power, it has been discovered, quite surprisingly. that electrodialytically and electrolytically processed kaolin, upon which methylene blue of FeSO is adsorbed, possesses electropositive character, the latter being substantially unobtainable with either the electrical processing or adsorption of methylene blue or FeSO, alone.

Natural kaolin particles are crushed to a particle size of 0.1 to 0.5 mm. and are subjected to electrical cleansing between a pair of platinum electrodes across which 10 volts are applied in the stilled water. A current density of 0.5 amp/cm. is provided and the vessel is subdivided by a cellophane membrane. Ions are found to pass from the kaolin particles into the water and to be removed from the compartment by dialysis to the membrane. Upon conclusion of dialysis, i.e., when the water in the other compartment is found to be substantially free from ions, the particles are rinsed with the distilled water and dried. The particles which are obtained are found to be less electronegative, i.e., to have a reduced tendency to drift toward a positive electrode, than the original particles and to have a slightly increased adsorptivity with respect to the tarry constituents of cigarette smoke. A portion of the particles is thereafter treated with methylene blue at a concentration of the order of hundredths of a millimole per mole of the particles while the balance are treated with a ferrous sulfate solution of similar concentration. The particles are again dried and are now found to be electropositive, i.e., to have a tendency to drift toward the negative electrode in an electrophoresis field. The adsorptive quality of the particles to the tarry constituency of cigarette smoke is substantially greater than that of the particles without adsorption of the cationizing compound, in fact, the adsorptivity increased by a order of magnitude.

The filter herein disclosed is, of course, capable of numerous modifications without departing from the spirit and scope of the invention as defined in the appended claims.

I claim:

1. The method of making an adsorber for the tarry constituent of cigarette smoke, comprising the steps of:

a. forming a body of mineral silicate particles selected from the group which consists of clay, kaolin and feldspar and having naturally occurring electronegative character;

b. at least partly removing the electronegative charge on said particles by subjecting same to an electrical treatment capable of removing ions from said particles and c. incorporating said particles in a tobacco-smoke filter.

2. The method defined in claim 1 wherein said electrical treatment is electrodialysis.

3. The method defined in claim 1 wherein said electrical treatment involves electrolysis.

4. The method defined in claim 1 wherein said electrical treatment is electrophoresis.

5. The method defined in claim 1 wherein said particles are incorporated in a filter in part by dispersing said particles throughout a mass of cellulosic fibers.

6. The method of making an adsorber for the tarry constituent of cigarette smoke, comprising the steps of:

a. forming a body of mineral silicate particles selected from the group which consists of clay, kaolin and feldspar and having naturally occurring electronegative character;

b. at least partly removing the electronegative charge on said particles;

b,. initially cleaning said particles in aqueous suspension to reduce the electronegative character of the particles;

b thereafter adsorbing a cationizing material on said particles to impart electropositive character thereto and c. incorporating said particles in a tobacco-smoke filter,

said cationizing substance being selected from the group which consists of methylene blue and ferrous sulfate.

7. The method defined in claim 6 wherein said particles are incorporated in a filter in part by dispersing said particles throughout a mass of cellulosic fibers.

8. A tobacco smoke filter comprising a charge of mineral silicate particles selected from the group consisting of clay, kaolin and feldspar having naturally occurring electronegative character, said charge being shaped to conform to the smoke passageway of a smoking article, the said particles having a reduced electronegative charge thereon by being subjected to electrical treatment operative to remove ions from the said particles, the filter particles being effective to adsorb tarry constituents from the smoke. 

2. The method defined in claim 1 wherein said electrical treatment is electrodialysis.
 3. The method defined in claim 1 wherein said electrical treatment involves electrolysis.
 4. The method defined in claim 1 wherein said electrical treatment is electrophoresis.
 5. The method defined in claim 1 wherein said particles are incorporated in a filter in part by dispersing said particles throughout a mass of cellulosic fibers.
 6. The method of making an adsorber for the tarry constituent of cigarette smoke, comprising the steps of: a. forming a body of mineral silicate particles selected from the group which consists of clay, kaolin and feldspar and having naturally occurring electronegative character; b. at least partly removing the electronegative charge on said particles; b1. initially cleaning said particles in aqueous suspension to reduce the electronegative character of the particles; b2. thereafter adsorbing a cationizing material on said particles to impart electropositive character thereto and c. incorporating said particles in a tobacco-smoke filter, said cationizing substance being selected from the group which consists of methylene blue and ferrous sulfate.
 7. The method defined in claim 6 wherein said particles are incorporated in a filter in part by dispersing said particles throughout a mass of cellulosic fibers.
 8. A tobacco smoke filter comprising a charge of mineral silicate particles selected from the group consisting of clay, kaolin and feldspar having naturally occurring electronegative character, said charge being shaped to conform to the smoke passageway of a smoking article, the said particles having a reduced electronegative charge thereon by being subjected to electrical treatment operative tO remove ions from the said particles, the filter particles being effective to adsorb tarry constituents from the smoke. 